Semiconductor devices may use discrete devices, such as a field effect transistors (FETS), as switching devices. In the transistor, an on-current formed in a channel between source and drain regions of the device typically determines the operating speed of the device. Normally, a planar-type transistor may be provided by forming a gate electrode and source/drain regions on a substrate on which a device will be formed, for example, an active region. A typical planar-type transistor has a planar channel between the source/drain regions. The on-current of the planar-type transistor is typically proportional to a width of the active region, and is typically inversely proportional to a distance between the source and drain regions, i.e., a gate length. Thus, in order to increase the operating speed of a device by increasing the on-current, a length of a gate is typically decreased, and a width of an active region is typically increased. However, increasing the width of the active region in the planar-type transistor may increase the overall size of the device, which may be incompatible with the trend in the semiconductor fabrication industries to develop semiconductor devices of increasingly higher integration density.
Furthermore, the planar-type transistor may experience a short channel effect when a distance between source and drain regions in the planar-type transistor is shortened. Therefore, generation of the short channel effect typically must be effectively suppressed in order to provide a transistor having a short channel length suitable for a next generation semiconductor device. However, since a conventional planar-type transistor, where a channel is formed in parallel with the surface of a semiconductor substrate, is a flat-type channel device, the structure may be unfavorable to the scale-down of the device, and it may be difficult to suppress generation of the short channel effect as well.
To address the problems of the short channel effect, and scale down the transistor, a transistor having a recessed channel has been proposed. The recessed channel transistor may include a recessed channel region and an insulated gate electrode. The recessed channel transistor may provide a relatively effective channel length compared to that of a planar-type transistor. In other words, the recessed channel transistor may provide a structure capable of solving the problems due to the short channel effect. However, the recessed channel transistor may have unfavorable defects compared to the planar-type transistor, such as an increased threshold voltage and/or operating speed.